In general, the present invention relates to medical fluid delivery systems that employ a disposable set with sterile fluid pathways. In particular, the present invention provides systems, methods and apparatuses for disposable set-based dialysis medical fluid therapies, including but not limited to those using peristaltic pumps, diaphragm pumps, pneumatic pumps and gravity.
Due to various causes, a person's renal system can fail. Renal failure produces several physiological derangements. The balance of water, minerals and the excretion of daily metabolic load is no longer possible and toxic end products of nitrogen metabolism (urea, creatinine, uric acid, and others) can accumulate in blood and tissue.
Kidney failure and reduced kidney function have been treated with dialysis. Dialysis removes waste, toxins and excess water from the body that would otherwise have been removed by normal functioning kidneys. Dialysis treatment for replacement of kidney functions is critical to many people because the treatment is life saving.
Hemodialysis (“HD”) and peritoneal dialysis (“PD”) are two types of dialysis therapies used commonly to treat loss of kidney function. HD removes waste toxins and excess water from the patient's blood. The patient is connected to a hemodialysis machine via catheters into a patient's vein and artery. Blood is pumped from the patient and through the inside of hollow, porous tubes of a dialyzer connected to the machine. The machine produces dialysate, which is pumped outside the hollow, porous tubes. A pressure gradient causes excess water to be pulled from the blood, through the pours of the membrane, into the dialysate, where it is carried away. Diffusion and osmosis causes waste and toxins to move thought the pours into the dialysate to be carried away. Cleaned blood is returned to the patient. A large amount of dialysate, for example about 120 liters, is consumed to dialyze the blood during a single hemodialysis therapy. HD lasts several hours and is generally performed in a treatment center about three or four times per week.
PD uses a dialysis solution, or “dialysate,” which is infused into a patient's peritoneal cavity via a catheter. The dialysate contacts the peritoneal membrane of the peritoneal cavity. Waste, toxins and excess water pass from the patient's bloodstream, through the peritoneal membrane and into the dialysate due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. The spent dialysate is drained from the patient, removing waste, toxins and excess water from the patient. This cycle is repeated.
There are various types of PD therapies, including continuous ambulatory peritoneal dialysis (“CAPD”), automated peritoneal dialysis (“APD”), tidal flow APD and continuous flow peritoneal dialysis (“CFPD”). CAPD is a manual dialysis treatment. The patient manually connects an implanted catheter to a drain, allowing spent dialysate fluid to drain from the peritoneal cavity. The patient then connects the catheter to a bag of fresh dialysate, infusing fresh dialysate through the catheter and into the patient. The patient disconnects the catheter from the fresh dialysate bag and allows the dialysate to dwell within the peritoneal cavity, wherein the transfer of waste, toxins and excess water takes place. The introduction of twin bag sets reduced the number of connections and disconnections by “Y-ing” the drain line and the fresh dialysate bag. Nevertheless, manual PD requires a significant amount of time and effort from the patient, leaving ample room for improvement. After a dwell period, the patient repeats the manual dialysis procedure, for example, four times per day, each treatment lasting about an hour.
APD is similar to CAPD in that the dialysis treatment includes drain, fill, and dwell cycles. APD machines, however, perform the cycles automatically, typically while the patient sleeps. APD machines free patients from having to manually perform the treatment cycles and from having to transport supplies during the day. APD machines connect fluidly to an implanted catheter, to a source or bag of fresh dialysate and to a fluid drain. APD machines pump fresh dialysate from a dialysate source, through the catheter, into the patient's peritoneal cavity, and allow the dialysate to dwell within the cavity, and allow the transfer of waste, toxins and excess water to take place. The source can be multiple sterile dialysate solution bags.
APD machines pump spent dialysate from the peritoneal cavity, though the catheter, to the drain. As with the manual process, several drain, fill and dwell cycles occur during APD. A “last fill” occurs at the end of CAPD and APD, which remains in the peritoneal cavity of the patient until the next treatment.
Both CAPD and APD are batch type systems that send spent dialysis fluid to a drain. Tidal flow systems are modified batch systems. With tidal flow, instead of removing all of the fluid from the patient over a longer period of time, a portion of the fluid is removed and replaced after smaller increments of time.
Continuous flow, or CFPD, systems clean or regenerate spent dialysate and thereby consume a lesser volume dialysate when compared to CAPD or conventional APD. Regeneration systems pump fluid into and out of the patient, through a loop. Dialysate flows into the peritoneal cavity through one catheter lumen and out another catheter lumen. The fluid exiting the patient passes through a reconstitution device that removes waste from the dialysate, e.g., via a carbon filter and a urea removal column that employs urease to enzymatically convert urea into ammonia. The ammonia is then removed from the dialysate by adsorption prior to reintroduction of the dialysate into the peritoneal cavity. Additional sensors are employed to monitor the removal of ammonia. CFPD systems are typically more complicated than batch systems.
Many PD systems use gravity to fill and drain. Patient data published by Brandes et al. shows that flow rates during fill cycle are relatively constant and related to the patient's position (supine>sit) and the absolute head height of the supply bag. Drain cycles however normally take about twice as long as fill cycles and have an antilog relationship with time. Within the drain cycle, about 80% of intra-peritoneum volume is drained within the first 40% of the total drain time. Similar results are found from patient data by Amici et al., and from patient trials for Baxter's HomeChoice and Quantum PD cyclers.
Flow rates of gravity fill and drain are functions of several physical parameters, including head heights to the patient's peritoneum, catheter type (resistances), tubing set type, etc. To overcome the fill and drain problems, some advanced APD machines use pumps to fill and drain. Pumps provide active fluid delivery but add complexity and cost. Accordingly, a need exists to provide a relatively low cost PD machine that combines desirable aspects of different types of APD systems.